Could a due date be this wrong ?

[TianaM23]

Heyy,

Could a due date be off by a whole month at a 12 week scan ?

Highly unlikely a scan would be that far out at that stage. I've had one out by 10 days but the rest much closer to lmp.

Not really. I was sent to my scan too early - I was only 10 weeks and had to go back again, they could see that straight away.

Never known a date to be that out.

I think typically by a 12 week scan the baby can be measured pretty precisely which is why they wait until that stage to date a pregnancy.

I could see it being out by days perhaps, but certainly not a whole month.

Not a whole month no. So I'd assume you have your date wrong and the scan is correct.

That would be unusual/unlikely. A few days up to a week either way, maybe.

Is the scan putting the date earlier or later than you expected?

More likely they got it right and you got the date of last period wrong, could be you had some bleeding you thought was a period?

Any due date before a scan goes on your last period but some women ovulate a different times of the month and if there's a hormonal contraception fail or recent use then that date can be estimated wrongly.
When I went for my 12 week scan I was only 9 weeks, I put it down to only having one period after coming off the pill and my cycle not being regular.
The scan will be correct though.

Which way did the scan delay your expected due date OP? Did it date you as 16 weeks or 8 weeks?

Scans are only accurate to plus or minus 7 days, ie a 14 day window, but I would think a month is so far outside that as to be impossible.

I went to my 12 week scan to be told I was only 8 weeks. The dates of my last period made me 12 weeks so not sure what happened x

@Bayjeetay
Presumably, if the scan was correct, you didn’t ovulate and conceive until 6 weeks after your last period rather than 2 weeks after.
I just don’t understand why they count that way.

It depends entirely on how long your cycles are and when you ovulate.

I think it depends when you got a positive test. If you thought you were 12 weeks and the scan said only 8 weeks but you didn't find out about the pregnancy until quite late (ie 8 weeks going but what you thought) then the scan is probably correct and you just ovulated late.